If $10$ bulbs of $100 \ W$ each are kept on for $1 \ \text{hour}$, how much electrical energy is consumed?

Derive the relation $R = R_{1} + R_{2} + R_{3}$ when three resistors $R_{1}, R_{2}$ and $R_{3}$ are connected in series in an electric circuit.

$(a)$ Define potential difference between two points in a conductor.
$(b)$ Name the instrument used to measure the potential difference in a circuit. How is it connected?
$(c)$ $A$ current of $2 \, A$ passes through a circuit for $1$ minute. If the potential difference between the terminals of the circuit is $3 \, V$, what is the work done in transferring the charges?

Electric current flows through three lamps when arranged in $(a)$ a series and $(b)$ a parallel circuit. If the filament of one lamp breaks,explain what happens to the other two lamps in both cases.

Define resistivity of a material.

The electrical resistivity of a few materials is given below in ohm-metre. Which of these materials can be used for making the element of a heating device?

$A$. $6.84 \times 10^{-8} \, \Omega m$

$B$. $1.60 \times 10^{-8} \, \Omega m$

$C$. $1.00 \times 10^{-4} \, \Omega m$

$D$. $2.50 \times 10^{12} \, \Omega m$

$E$. $4.40 \times 10^{-5} \, \Omega m$

$F$. $2.30 \times 10^{17} \, \Omega m$